HFA3860 Datasheet, PDF (13/40 Pages) Intersil Corporation – 11 Mbps Direct Sequence Spread Spectrum Baseband Processor

HFA3860
Table 7 shows examples of the bit rates and the symbol
rates and Figure 8 shows the modulation schemes.
The modulator is completely independent from the
demodulator, allowing the PRISM baseband processor to be
used in full duplex operation.
DATA
MODULATION
DBPSK
DQPSK
BMBOK
QMBOK
TABLE 7. BIT RATE TABLE EXAMPLES FOR MCLK = 44MHz
A/D SAMPLE CLOCK
(MHZ)
TX SETUP CR 20
BITS 1, 0
RX STATUS CR 24
BITS 7, 6
DATA RATE (Mbps)
44
00
00
1
44
01
01
2
44
10
10
5.5
44
11
11
11
SYMBOL RATE
(MSPS)
1
1
1.375
1.375
DATA
802.11 DSSS BPSK
1 MB/S
BARKER
802.11 DSSS QPSK
2 MB/S
BARKER
1 BIT ENCODED TO ONE OF
2 CODE WORDS
(TRUE/INVERSE)
2 BITS ENCODED
TO ONE OF
4 CODE WORDS
IOUT
QOUT
CHIP
RATE
SYMBOL
RATE
11 CHIPS
11 MC/S
1 MS/S
11 CHIPS
11 MC/S
1 MS/S
I vs Q
5.5 MB/S BMBOK
MODIFIED
WALSH FUNCTIONS
11 MB/S QMBOK
MODIFIED
WALSH FUNCTIONS
4 BITS ENCODED TO ONE OF
16 MODIFIED WALSH
CODE WORDS
8 BITS ENCODED TO
ONE OF
256 MODIFIED WALSH
CODE WORDS
8 CHIPS
11 MC/S
1.375 MS/S
8 CHIPS
11 MC/S
1.375 MS/S
FIGURE 8. MODULATION MODES
Header/Packet Description
The HFA3860 is designed to handle continuous or
packetized Direct Sequence Spread Spectrum (DSSS) data
transmissions. The HFA3860 generates its own preamble
and header information.
The device uses a synchronization preamble of up to 256
symbols, and a header that includes five fields. The
preamble is all 1's (before entering the scrambler). The
actual transmitted pattern of the preamble will be
randomized by the scrambler. The preamble is always
transmitted as a DBPSK waveform.
The five fields for the header shown in Figure 9 are:
Service Field (8 Bits) - This field is currently unassigned
Start Frame Delimiter (SFD) Field (16 Bits) - This field
carries the synchronization to establish the link frame timing.
The HFA3860 will not declare a valid data packet, even if it
PN acquires, unless it detects the SFD. The HFA3860
receiver is programmed to time out searching for the SFD via
CR15. The timer starts counting the moment that initial PN
synchronization has been established from the preamble.
Signal Field (8 Bits) - This field indicates what data rate the
data packet that follows the header will be. The HFA3860
receiver looks at the signal field to determine whether it
needs to switch from DBPSK demodulation into DQPSK or
B/QMBOK demodulation at the end of the always DBPSK
preamble and header fields.
and can be utilized as required by the user. Set to 00h for
4-13